The invention relates to a screening machine having striking elements which can act on the lower face of the screen and which by means of a tube connected to them, extending over the length of the screen and connected to a drive, cause the screen to perform a vibrating movement.
With known mountings both end parts of the striking elements are mounted in the screen frame with the aid of rubber bushes. Another form of construction is described in German Gebrauchsmuster No. 7,206,763 and achieves a certain improvement by utilizing a self-aligning bearing. Neither of these known arrangements is satisfactory. In order to achieve a screening effect very fine screen fabrics must be vibrated at high frequencies. Since a high driving power is required to vibrate the entire screen box at high frequencies, the expedient has been adopted of using a stationary screen box and vibrating the screen fabric directly by means of striking elements. Striking elements of this kind are described for example in Austrian Patent Specification No. 322,477. Another form of construction of the striking elements is shown in Austrian Patent Specification No. 301,471. These two forms of construction have the common disadvantage that the striking elements perform a rotary movement and thus chafe the screen at the point of contact, particularly in the case of small-mesh screens.
Another disadvantage of known mountings is the rubber bush at the center of rotation of the tube vibrating about it, since this bush becomes unusable after a short time as the result of wear.